1. Field of the Invention
The present invention relates to a casing for containing cameras, videocameras, flashlights, portable radios and other articles which can be used in scuba diving or a casing of such an article.
2. Description of the Prior Art
As is well known, scuba divers carry cameras, videocameras, flashlights, portable radios and other articles which can be used in scuba diving. These articles have a watertight casing, or they are contained in a separate watertight casing. Such casing must have a pressure resisting characteristic in addition to watertightness. The water pressure will increase 1 atm. for each increase of 10 meter depth. Recently, scuba divers are likely to swim at an increased depth, and therefore, the casing must be designed to have a good pressure resistance. Hitherto, in an attempt to assure the watertightness in such casings, improved packings have been proposed and actually used. Also, in an attempt to give a good pressure resistance to such casings the casing wall structure has been designed so as to have a good rigidity. This, however, has the following demerits:
1) The casing frame must be designed so as to have an increased rigidity. The resultant elaborate frame requires an increased number of parts and manufacturing steps. Accordingly the manufacturing cost increases. PA1 2) In case the casing frame cannot be designed appropriately for the purpose of increasing its pressure resistivity, this problem must be solved with recourse to appropriate selection of material. This, however, is likely to limit selection of material from the angle of pleasing shape, accordingly reducing the freedom with which a casing can be designed. PA1 3) An attempt to provide the pressure resistivity as much as required by increasing the rigidity of the casing wall will cause increase of the weight of the casing. Such casings are not difficult to handle in water, but they are different to carry to a scuba diver place on land.